Patent GB-406775-A (GB)
Title: Improvements in electric withdrawable switchgear
IPC: H02B11/18
Filed: 1932-09-27
Abstract: 406,775. Switchgear structures; oilbreak switches. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and KEELEY, F. J., c/o General Electric Co., Witton, Birmingham. Sept. 27, 1932, No. 26819. [Class 38 (v).] In withdrawable switchgear of the duplicate busbar type for selectively connecting a cable to either of two sets of busbars and in which the cable consists of split conductors 5 for protective purposes, each terminal 11, 12, Figs. 1 and 2, of the circuit-breaker is provided with a pair of plugging contacts adapted to engage the split conductors 5 and extend them separately, through conductors 13 in the terminals, to the break contacts 14, 15 of the circuit-breaker, and means are provided for connecting together the conductors 13 for the time being associated with the cable to parallel the split conductors of the cable before the associated break contacts are energized. In one arrangement, shown diagrammatically in Fig. 1, the cable spout 1 is placed between spouts 2, 3 associated with the respective sets of busbars, and each of the conductors 13, in addition to being connected with the main contacts 14 and arcing contacts 15 of the circuit-breaker, is connected to an additional contact 16. The moving contact arm 17 of the circuit breaker carries a pair of bridging contacts 18, each adapted to connect together the extra contacts on each terminal of the circuit-breaker, before the associated break contacts are engaged by the corresponding moving contacts. In another arrangement, Fig. 2, the extra contacts are dispensed with, and the arcing contacts 15 associated with the terminal 12 connected to the cable are so arranged that, on closing the circuit-breaker, they engage the movable contact member 17 before the arcing contacts 15 associated with the terminal 11 connected to the busbars. This result is obtained by mounting both sets of arcing contacts on a movable rod 19 which, in the case of the terminal connected to the busbars, can pass freely under the action of a spring 20 through an aperture in a member 21 secured to the busbar spouts 2, 3, but, in the case of the terminal connected to the cable, the rod engages the member 21 and is thereby moved against the action of the spring to effect the required movement of the contacts 15. A construction for carrying out the arrangement of Fig. 1 is shown in Fig. 3, the terminal being shown connected to the cable. The split conductors in the terminal comprise a rod 25 connected to a pair of plugs 28, and a tube 24 connected to a pair of plugs 29, the rod and tube being mounted in an insulating tube 22. The split conductors of the cable comprise a rod 37 connected to sockets 34 adapted to be engaged by the plugs 28, and a tube 36 connected to sockets 31 for engagement by the plugs 29, the arrangement being such that the inner and outer conductors of the terminal are transposed through the plugs and sockets and connected respectively to the outer and inner conductors of the cable. At their lower ends, the conductors 24, 25 are connected to contact carriers 38, 39, the former carrying the main contacts 43 and an extra pair of contacts 44, while the carrier 39 has main contacts 45, arcing contacts 47 and an extra pair of contacts 46. The movable bridging member 49 of the circuit-breaker carries an insulated bridging contact 51 adapted to engage the contacts 44, 46, on closing the circuit-breaker, before the arcing contacts 47 enter into engagement with contacts 50 on the bridging member 49. In carrying out the arrangement of Fig. 2, the inner rod conductor of the terminal is slidably mounted within the outer tubular conductor and carries the arcing contacts at its lower end. When the terminal is plugged into the cable sockets, this rod engages an abutment and is pressed down, against the action of a spring, to give the desired lead to the arcing contacts on the cable side.